The present invention claims priority to its priority documents No. 2001-156508 and No. 2001-184725 filed in the Japanese Patent Office on May 25, 2001 and Jun. 19, 2001, respectively, the entire contents of which are expressly incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical device for bar-code reading and a method for manufacturing thereof, in particular to those capable of improving the individual degrees of freedom in design and positioning accuracy of a light projection lens and a light receiving lens in an integrated constitution and also to a light projection/receiving package for bar-code reading, and in particular for improving the downsizing of the package through minimizing an area for mounting a light emitting element and a receiving element.
2. Description of the Related Art
Many recent shops and factories practice sales management of commodities or production management of products by attaching thereto bar codes indicating digital information of the products and by reading such information through optical scanning thereof. In a general procedure using such kinds of bar codes, light is irradiated to a bar code and reflected light therefrom is processed by photo-electric conversion, depending on the intensity of the reflected light, to thereby decode the information based on a combined pattern of detected signals.
More specifically, as schematically shown in FIG. 19, a light projection lens 3 focuses light emitted from a light emitting element 1, and thus focused light is irradiated to a bar code 9 after being reflected off a mirror 7 of a scan mirror 5. Mirror 7 is swung so as to irradiate the entire area of bar code 9. The swinging of mirror 7 is based on attraction and repulsion of a magnet 11 attached to mirror 7 to or from a drive coil 13 into which magnet 11 is inserted, where drive coil 13 is applied with positive and negative currents inverting at a predetermined cycle to thereby swing mirror 7 around a fulcrum of swinging 15.
The light irradiated on a surface of bar code 9 returns back to mirror 7 with an intensity variation caused by a black-and-white pattern of bar code 9 while being affected by some irregular reflection. A condensing lens 17 then focuses the light reflected there, and a light receiving element 19 electrically converts the intensity variation to produce an output. Light receiving element 19 is provided on a front surface with a band-pass filter (BPF) 21 for improving accuracy in the reading, to thereby successfully prevent unnecessary light having a frequency other than the emission frequency from being caught.
There has been provided an optical device for bar-code reading, as shown in FIG. 20 which materializes such reading systems. As illustrated in FIG. 20 , the device comprises a light emitting assembly A having a light emitting element 1 and a light projection lens 3 housed in a casing 25, and a light receiving assembly B having a light receiving element 19, a light receiving lens 17 and a BPF 21 housed in a casing 27, both assemblies being mounted on a substrate 29. Electrical connections within individual casings 25 and 27 are accomplished through wire bonding or the like. Mirror 7 of scan mirror 5 is arranged so as to allow swinging around the fulcrum of swinging 15. Light emitting assembly A, light receiving assembly B and scan mirror 5 are housed in a housing not shown, to thereby form an optical device for bar-code reading.
The foregoing optical device for bar-code reading however, requires a large mounting space and can attain only a limited range of downsizing since light emitting assembly A having light emitting element 1 and the light projection lens 3 housed in casing 25, and light receiving assembly B having, light receiving element 19 and light receiving lens 17 in casing 27 are separately composed.
As measures for solving such non-conformity, there is known a xe2x80x9cbar-code readerxe2x80x9d as disclosed in Japanese Patent Application Publication No. Hei 7-93454, in which two lens portions are integrated into one transparent lens to thereby downsize a device as a whole, and a xe2x80x9cbar-code reading devicexe2x80x9d as disclosed in Japanese Patent Application Publication No. Hei 11-15910, in which an irradiation lens and an imaging lens are formed using a transparent resin material in an integrated manner to thereby reduce the number of optical parts and save labor for assembly.
While these devices were successful in achieving a certain degree of space saving, it has not been allowable to choose different media as being optimized for the light emitting characteristics and the light receiving characteristics, since the light projection lens portion and the light receiving lens portion are molded in an integrated manner within a single kind of transparent resin used as a medium. It also has been difficult to compose either lens as a compound lens or to provide different coatings for the individual lenses, which has limited the design of such lenses. Still another problem resides in that this kind of integrated mold lens cannot allow movement of either lens once the other lens is properly positioned and fixed, which inhibits precise positioning by finely adjusting positions of both lenses on the light emitting side and the light receiving side.
An electro-optical reading device, as disclosed in, Japanese Patent Application Publication No. Hei 11-326805, is such that it has a semiconductor laser chip (light emitting element) and a photo detector (receiving element) mounted side by side on one surface of a printed circuit board, where all of which are covered with a mold resin member. To the mold resin member, a lens, a prism and an opening are molded in an integrated manner so as to allow the laser light from the semiconductor laser chip to be focused, bent in the optical path thereof and emitted, and, further, having a concave mirror for focusing the returned light towards a photodetector, to thereby achieve downsizing and weight reduction. The device, however, inevitably has a large printed circuit board due to the planar arrangement of the semiconductor laser chip and photo-detector side by side on one surface of the printed circuit board, so that downsizing cannot be attained
The present invention was proposed considering the foregoing situation and provides an optical device for barcode reading capable of improving the degree of freedom in design of the component lenses so as to allow free positional adjustment of such lenses while ensuring a small size and light weight of the device per se and a method for manufacturing thereof.
Furthermore, the present invention also was proposed considering the foregoing situation and provides a light projection/receiving package in which keeping an area sufficient for the mounting of either one of a light emitting element and a receiving element enables mounting of the other element to thereby achieve downsizing and weight reduction of the package.
As has been detailed in the above, since the light projection/receiving package according to the second aspect of the present invention is composed so that a light emitting element and a light receiving element are mounted back to back on front and rear planes of a single die pad, it is not necessary to keep both areas for mounting the light emitting element and the light receiving element on one plane (on the same plane) of the die pad. Accordingly, it will be sufficient to use a die pad affording a mounting area for either element requiring a larger mounting area, and this intrinsically allows mounting of the other element on the opposite plane. That is, only a small die pad affording a mounting area for either the light emitting element or the light receiving element allows the mounting of both. This successfully results in downsizing and weight reduction of the
An optical device for bar-code reading according to a first aspect of the present invention comprises a light emitting element; a light projection lens; a light receiving lens; and a receiving element. The light projection lens focuses light from the light emitting element so as to irradiate a bar code. The light receiving lens focuses reflected light from the bar code and has formed therein a penetrating hole penetrating a plane of incidence of light and a plane of outgoing of light, in which the light projection lens is inserted. The light receiving element receives the light focused by the light receiving lens so as to perform photo-electric conversion.
In the optical device for bar-code reading, a space for mounting the light receiving lens essentially includes a space for mounting the light projection lens by forming a penetrating hole through the light receiving lens and by inserting the light projection lens into the penetrating hole. Accordingly, it is not necessary to provide a mounting space for every lens, which results in downsizing and weight reduction. In addition, it allows the selection of a material and a coating optimized for each lens, to thereby expand the possibilities in design. It also is advantageous in that the positions of the light projection lens and the light receiving lens can be adjusted independently so that positional errors of the individual lenses relative to the individual elements (light emitting element and receiving element) can surely be absorbed.
The optical device for bar-code reading of the first aspect of the invention may be modified so that the light projection lens thereof is a compound lens in which a plurality of single lenses are combined.
In the optical device for bar-code reading, the light projection lens is composed as a compound lens. The compound lens comprises a plurality of single lenses combined with each other. In this case, typically composing the compound lens so that light can propagate almost in parallel between two lenses will ensure a large allowance for axial dislocation in a direction normal to the optical axis, which is effective in terms of improving production yield and reliability.
The optical device for bar-code reading also may be further modified so that the plurality of single lenses are fitted within a cylinder. They are arranged so that an optical axis of the lenses coincide with an axis of the cylinder, and the cylinder is inserted in the penetrating hole of the light receiving lens.
Since the optical device for bar-code reading is composed so that a plurality of single lenses are fitted within a cylinder and the cylinder is inserted in the penetrating hole of the light receiving lens, a variety of positional adjustments of the lenses will be available, for example, for moving the whole compound lens, previously fabricated so as to arrange the single lenses within the cylinder at regular intervals relative to the penetrating hole, or moving an arbitrary single lens relative to the cylinder while keeping the cylinder fixed in the penetrating hole.
The optical device for bar-code reading may be further modified so that the cylinder is made of a metal.
As for the optical device for bar-code reading, composing the cylinder with a metal can desirably prevent the light which comes from the light emitting element and goes into the compound lens from propagating from an inner circumferential surface of the penetrating hole towards a medium of the receiving lens. Accordingly, it is not probable that the light from the light emitting element will come into the receiving element to cause disturbance. In other words, the receiving element can gain a higher receiving accuracy of the reflected light.
The optical device for bar-code reading of the first aspect of the invention also may be modified so that the light projection lens is a cylindrical single lens.
As for the optical device for bar-code reading, composing the light projection lens with the cylindrical single lens can facilitate the manufacturing thereof as compared with that of the forgoing compound lens. The cylindrical shape allows the light projection lens to be inserted into the penetrating hole, so that the light projection lens is now attachable to the light receiving lens in a manner freely movable along the optical axis without using any other members (the foregoing cylinder, for example).
The optical device for bar-code reading modified as above may be further modified to have a columnar heat sink provided so as to coincide the axis thereof with an optical axis of the light receiving lens. The heat sink has fixed on one end plane thereof the light receiving element and has fixed on the side plane thereof the light emitting element.
In such optical device for bar-code reading, the light receiving element fixed on one end plane of the heat sink opposes with the light receiving lens on the optical axis thereof. This means that the optical device can receive focused light from the light receiving lens in an efficient manner. On the other hand, the light emitting element fixed on the side plane of the heat sink can desirably prevent the light from the light emitting element from going into the entire portion of the light receiving lens, which allows irradiation of the light only in a portion of the receiving lens having incorporated therein the light projection lens. Accordingly, the light emitted from the light emitting element and reflected from a bar code after irradiation can be directly received by the light receiving element attached on the heat sink without the need of a 90xc2x0 bending of the optical path using a mirror or the like.
A method for manufacturing an optical device for bar-code reading according to the first aspect of the present invention is characterized by comprising the steps of fitting a light projection lens into a penetrating hole formed in a receiving lens so as to penetrate a plane of incidence of light and a plane of outgoing light in a manner freely movable along the optical axis of the light projection lens fixing the light receiving lens after positioning it relative to a light receiving element and fixing the light projection lens after positioning it relative to the positioned and fixed light receiving lens.
In the manufacturing method, the light projection lens is positioned by moving it relative to the light receiving lens after positioning and fixing the light receiving lens relative to the light receiving element. Accordingly, moving the light projection lens to be performed later will never dislocate the light receiving lens, which is positioned in advance. In other words, the individual lenses can be positioned at optimum positions. This allows the individual lenses to be finely positioned, which has not been practical for the conventional, integrated mold lens: and, is can improve accuracy in assembly of the optical device for bar-code reading and in reading while concomitantly attaining downsizing and weight reduction.
A light projection/receiving package according to a second aspect of the present invention is such that for irradiating light emitted from a light emitting element to a target object to be irradiated, and for receiving reflected light from the target object using a light receiving element, it is characterized in that the light emitting element and light receiving element are mounted on front and rear planes of a single die pad.
Since the light projection/receiving package is composed so that the light emitting element and the light receiving element are mounted back to back on the front and rear planes of the single die pad, it is not necessary to keep both areas for mounting the light emitting element and the light receiving element on one plane (on the same plane) of the die pad. This means that it will be sufficient to use a die pad affording a mounting area for the light receiving element, which generally requires a larger mounting area, and this intrinsically allows mounting of the light emitting element on the opposite plane. Accordingly, the die pad in this case ill be smaller than that having on one plane both of the light emitting element and the light receiving element. This successfully results in downsizing and weight reduction of the light projection/receiving package.
The light projection/receiving package according to a third aspect of the present invention is characterized by comprising a die pad a light emitting element and a light receiving element respectively mounted back to back on the front and rear planes of the die pad an optical path bending means provided on one plane of the die pad on which the light emitting element is mounted so as to bend an advancing direction of the emitted light from the light emitting element approximately at right angles and a penetrating hole formed in the die pad so as to allow the light having the advancing direction bent by the optical path bending means to pass through towards the other plane of the die pad on which the light receiving element is mounted.
In the light projection/receiving package, when the light emitted from the light emitting element in a direction parallel to the plane of the die pad comes into the optical path bending means, the optical path thereof is bent approximately at right angles so as to have a direction perpendicular to the plane of the die pad. The directed light passes through the penetrating hole formed in the die pad to thereby reach the plane opposite to that having the light emitting element mounted thereon, that is the plane having mounted thereon the receiving element. Accordingly, the optical path of the light from the light emitting element can be bent towards the opposite plane within a limited area on the die pad plane, without providing any optical means for bending the optical path outside the die pad.
The light projection/receiving package may be modified further to comprise an integrated light projection/receiving lens having integrated therein a source lens portion and a light receiving lens portion that is provided in parallel to the die pad on the side facing to the plane thereof on which the light receiving element is mounted.
In the light projection/receiving package, the light emitted after passing through the penetrating hole is focused by the light projection lens portion and then irradiated to the target object to be irradiated. The reflected light returned back from the target object is focused by the light receiving lens portion and then goes into the light receiving element. In other words, only one integrated light projection/receiving lens portion is responsible for focusing the emitted light and the reflected light, which is beneficial in that it reduces the number of parts for the optical means and the man-hours for the assembly. Since the emitted light and the reflected light are directed perpendicular to the die pad, the light projection/receiving package also is advantageous in that only a simple assembly of the integrated light projection/receiving lens on the die pad in parallel thereto can readily align the center axes of the light projection lens portion and the light receiving lens potion in parallel to the optical axes of the emitted light and the reflected light.
The light projection/receiving package may further be modified so the receiving element is provided in the number of two, the die pad has the penetrating hole between the two light receiving elements, the integrated light projection/receiving lens has the receiving lens portion in the number of two, and the light projection lens portion is formed between the two light receiving lenses.
The light projection/receiving-package has two light receiving elements and two light receiving lens portions on one plane of the die pad, which successfully improves light receiving sensitivity. Since the penetrating hole is formed in the die pad between both light receiving elements and the light projection lens portion is formed between the light receiving lens portions, the package also is advantageous in that it provides the light emitting assembly only within a space for forming the light receiving assembly. Accordingly, such constitution in which the light emitting element and the light receiving element are mounted on the front and rear planes will more efficiently contribute to space saving.
The light projection/receiving package of the third aspect of the invention may be modified so that the package has a front wall in parallel to the die pad on the side facing to the plane thereof on which the light receiving element is mounted-and the light projection lens opposed to the penetrating hole and the light receiving lens opposed to the light receiving element are separately provided on the front wall.
The light projection/receiving package has the light projection lens and the light receiving lens in a separated manner, which is beneficial in that it completely prevents generation of extraneous light (stray light) caused by diffraction or dispersion from the light projection lens portion towards the light receiving lens portion. The extraneous light is likely to generate for a case in which the integrated light projection/receiving lens made of a single kind of medium is used. The separate provision of the light projection lens and the light receiving lens allows material selection and coating to be optimized for the individual lenses, which raises the degree of freedom in lens design and also allows independent positional adjustment thereof, which improves accuracy in the adjustment.
The light projection/receiving package may be modified further to comprise a partition wall formed between the die pad and the front wall of the package so as to isolate an emissive optical path spade between the penetrating hole and the light projection lens from an incident optical path space between the light receiving lens and the light receiving element.
Since the emissive optical path space and the incident optical path space are isolated by the partition wall in the light projection/receiving package, the light emitted from the penetrating hole will never leak from the emissive optical path space to the incident optical path space. This arrangement completely prevents the light emitted from the light emitting element from becoming the extraneous light for the light receiving element. This improves the light receiving sensitivity.